1. Field of the Invention
The present invention relates to a cold-forming steel article, in particular a tool with a large tempering depth or high full quenching and tempering capacity, which contains the alloying elements carbon, manganese, silicon, chromium, molybdenum, vanadium and tungsten, optionally the element niobium, as well as accompanying elements with a content of less than about 0.4% by weight, the remainder being contaminants and iron.
In particular, the invention relates to a tool that is coated with hard material at a temperature of higher than about 500° C.
2. Discussion of Background Information
Cold-forming steels are alloys that in the heat-treated state have a property profile with great hardness, high wear resistance and high material toughness, wherein a good workability and special dimensional stability during hardening and tempering represent important criteria. These cold-forming steels are used among other things as tools in punching technology of plastic molding for fine blanking as die parts and the like. In terms of alloying, these cold-forming steel materials are generally designed for tool production and the principal stress criteria in practical use.
A hardness of preferably at least about 60 HRC and a high carbide content with uniform distribution of the carbides in a high-strength matrix of the material are important for a high wear or abrasion resistance and a high dimensional stability of tools. However, it should be possible to use a simple tempering technology for the parts, wherein a desired deep hardness generation of the material under the quenching surface is necessary.
For tools or parts on which a particular hard material layer, e.g., a nitride, carbonitride or oxidecarbide layer of the elements titanium, chromium, aluminum and the like, is to be applied at a coating temperature of higher than 500° C., furthermore the substrate, that is, the cold-forming steel article, must withstand this thermal stress over the necessary or required coating period or must not exhibit a major decrease in the property values, in particular the hardness and toughness of the material.
In view of the requirements regarding a comprehensively improved property profile in a cold-forming steel article, it would be advantageous to have available a heat-treated material which from conventional temperatures which are easily set between about 1030° C. and about 1080° C. with intensified cooling to large depths is converted into a martensitic microstructure, provides high material hardness and toughness during tempering and is resistant to softening up to temperatures of over 500° C. with treatment times of up to several hours and has a high wear resistance.